In simple terms, animals such as cattle may be considered as processors of raw materials to a desired end product, namely, the conversion of feed to food, such as meat, milk, etc. In modern times, with increasing costs of animal feed, great effort is being expended to increase the efficiency of conversion of the feed to the desired product by the animal. The basic aim is to provide the animal with a totally balanced diet, i.e. with a daily ration which contains (a) the maximum amount of protein (natural or otherwise) and other essential nutrients which the animal is able to use beneficially, i.e. convert into desired products and utilize to sustain its normal life-sustaining functions and (b) sufficient energy-providing materials to enable the animal to effect the desired conversion to maximize its physical and economic efficiency in converting feed to food. It should be noted that the ration may be deficient, i.e. either lacking in energy-providing materials, in which case the animal is not able to optionally utilize the other components of the feed, or there may be an excess of energy-providing materials, caused for example, by insufficient protein in the ration, and in both cases the rate/degree of feed conversion will obviously suffer. Moreover, there is obviously a limit as to how much conversion an animal may effect in a set period of time, and providing feed over and above that required to effect the maximum possible feed conversion is wasteful and uneconomic. However, the amount and nutritional quality of the feed material available to the farmer from his own resources is generally fairly restricted. It is therefore common for the farmer to be assisted by an animal nutritionist whose task it is to formulate a ration which will provide the animals with all the material necessary to enable them to achieve maximum feed conversion most economically. Ideally, the calculated ration will utilize as far as possible the feed material the farmer has readily available to him and nutritional deficiencies therein are corrected by adding thereto an animal feed supplement containing the deficient nutritional components. Many such feed supplements are available to the farmer and contain, for example, protein, natural or N.P.N. (such as urea), carbohydrates, fats; vitamins such as vitamins A, B, C, D and E, and many trace elements such as calcium, phosphorous, copper, etc. The presently available prior art feeds are usually solids, solutions or slurries. In general, solid supplements are not as convenient as liquid supplements which may be conveniently pumped and are generally easier to handle. In the case of slurries, it is essential that the farmer have available to him on the farm, mixing apparatus for reforming the slurries into a homogeneous mixture before the feed is given to the animals. If this is not effected, and a non-homogeneous mix is given to the animals, there is a risk that some animals will obtain a "weak" feed, i.e. their diet will be deficient in some components, which is obviously undesirable, but a more real danger is that some animals would be fed an overrich diet which may result in their being poisoned or otherwise injured by the excess of certain materials. On the other hand, since some essential food ingredients are insoluble in an aqueous medium, supplements which are pure solutions usually need to be used in combination with a further, and solid, supplement. In the past, attempts to formulate supplements in suspension form have not proved commercially successful because, inter alia, gravitationally stable suspensions having a suspended solids content of a high enough value from a commercially practical viewpoint have not been attainable.
Additionally, the protein content, i.e. natural protein content, in known liquid feed supplements is obtained from many sources, such as fish solubles, fermentation solubles and dried brewers' yeast. In recent times there has been much investigation into the use of such materials because these are presently available in large amounts as industrial by-products. Of particular interest in the present instance is brewers' yeast. In the brewing process when fermentation has ceased, the fermenter vessel contents are cooled resulting in the yeast settling to the bottom of the vessel. The supernatant beer is transferred to storage and the yeast removed as a slurry in (green) beer, i.e. in aqueous alcohol. In the past this material has generally been converted into the corresponding dried product. However, there have been some attempts to use this material in wet slurry form-- see for example, an article by Dr. J. H. Linton entitled, "Utilization of Brewery By-Products as Livestock Feed" in the Master Brewers' Association of America Technical Quarterly, Vol. 10, No. 4, 1973 and Canadian Pat. No. 959,332. However, for various reasons there has not been widespread utilization of yeast slurries, although recent significant progress has been made in this area --refer to copending application Ser. No. 637,127, filed on Dec. 3. 1975 in the name of J. D. Harvey and R. C. Chalk, assigned to the present assignees, which discloses a liquid animal feed supplement comprising a specially treated form of spent brewers' yeast. As discussed in the specification of that copending application, the novel supplement has significant advantages over known liquid supplements. However, it still suffers from the disadvantage that the individual user must have mixing equipment available to ensure homogenization of the supplement prior to its being offered to the animals, generally by being applied to the roughage of the ration. If necessary, other components of which the ration is deficient are offered separately to the animals.